Final answer:
The dimension of each vector space is determined by the number of independent entries in the matrices.
Step-by-step explanation:
Dimension of each vector space:
- The vector space of all diagonal n x n matrices has dimension n.
- The vector space of all symmetric n x n matrices has dimension n(n+1)/2.
- The vector space of all upper triangular n x n matrices has dimension n(n+1)/2.
In each case, the dimension is determined by the number of independent entries in the matrices.